Powerful winter storms that strike the U.S. West Coast often occur in series, like the ones that recently raked Washington, Oregon, and California. These storms have their counterparts in the North Atlantic Ocean, and scientists supported in part by the National Science Foundation (NSF) are hot on their trail.
A major field program involving atmospheric researchers from 11 countries is straddling the Atlantic Ocean from Newfoundland to Ireland to study fierce winter storms that move eastward across the ocean and pound western Europe. Participating scientists include researchers from the National Center for Atmospheric Research (NCAR) in Boulder, Colorado. The project is called the Fronts and Atlantic Storm Track Experiment (FASTEX). Operations began on January 6 and will continue through February.
"The findings should lead to better forecasts for the west coasts of both Europe and North America, as well as a better understanding of how oceanic winter storms affect world climate," says Steve Nelson, program director in NSF's division of atmospheric sciences.
Forecasting the development of oceanic storms is still a challenge, largely because there are fewer weather observations at sea than over land. Cyclones (low-pressure centers) tend to develop along slow-moving cold fronts that extend across the Atlantic. The cyclones often develop midway between North America and Europe and reach their peak strength a day or two later near the British Isles.
FASTEX researchers are hoping to identify precursors that may trigger cyclones once the precursors overtake the cold front. These precursors could include jet streaks (regions of higher wind speed inside the jet stream) and pockets of air that descend from the stratosphere. If such precursors can be located as they reach the North Atlantic, the cyclones they later generate might be better forecast up to two or three days in advance. To follow the life cycles of precursors and cyclones, a wide array of observational tools will stretch from continent to continent and extend from midlatitudes to polar regions.
Although the geography of the Pacific Ocean differs from that of the Atlantic, some insights from FASTEX will be applicable to both. For instance, precursors beginning over Asia are likely responsible for some cyclones that reach the U.S. West Coast several days later. Techniques developed in FASTEX for identifying precursors and targeting observations could help to improve forecasts for both North America and Europe. A follow-up field experiment is being considered for the North Pacific.
FASTEX results may lead to a model for everyday weather monitoring in the future, according to Nelson. Computer models of the atmosphere (the main source of forecasting guidance) require a detailed picture of current weather in order to extend that picture into the future. Where data are limited-such as over the oceans-it may be worthwhile to focus data collection on a small area where storms are developing, rather than on a bigger area where relatively little is happening. Two major goals of FASTEX are to develop better techniques for targeting these sensitive regions, and to measure how much the targeting will improve computerized forecasts. Says Nelson, "Research on these targeting strategies is at a very early stage, but it has the potential to bring about revolutionary changes in weather forecasting."